I would do it as early as you can (so it is just done) and just store them in a plastic bag so they will stay fresh.

Yes, I am doing this too--stripping any ones as I get them FSOT, I really like to HEAT up the 2nd hand ones to get the soap out. Then I will probably toss the whole stash in a light wash and rinse just near end of July. But I will know they are basically already ready before then.

ETA: here's a link to pics of most of my nb and small stash, minus the flats and prefolds and KL0s that need fixing.